In the fields of chemistry, biology, materials science, microelectronics, optics, and medicine, the development of devices that are small relative to the state of the art and that are conveniently and relatively inexpensively reproduced is important.
A well-known method of production of devices, especially in the area of microelectronics, is photolithography. According to this technique, a negative or positive resist (photoresist) is coated onto an exposed surface of an article. The resist then is irradiated in a predetermined pattern, and portions of the resist that are irradiated (positive resist) or nonirradiated (negative resist) are removed from the surface to produce a predetermined pattern of resist on the surface. This is followed by one or more procedures. According to one, the resist serves as a mask in an etching process in which areas of the material not covered by the resist are chemically removed, followed by removal of resist to expose a predetermined pattern of a conducting, insulating, or semiconducting material. According to another, the patterned surface is exposed to a plating medium or to metal deposition (for example under vacuum) followed by removal of resist, resulting in a predetermined plated pattern on the surface of the material. In addition to photolithography, x-ray and electron-beam lithography have found analogous use. Lithography techniques such as those and are relatively labor intensive. The techniques require the design and fabrication of chrome masks, access to clean rooms, and the like.
Microelectromechanical systems are an area of relatively intensive research. These systems involve the fabrication of micro-scale structures prepared from silicon, or occasionally from other material such as gallium arsenide, metals, glasses, ceramics, or plastics, by typical integrated circuit industry microfabrication techniques such as photolithography or additive/subtractive processes such as deposition and etching. While interesting systems have been developed, simplification and increased versatility would be advantageous.
Carbon structures such as glassy carbon have numerous laboratory, metallurgical, mechanical, and electrical applications. Glassy carbon has found extensive use in connection with products such as beakers, joints, frits, brushes, contacts, furnace jigs and fixtures, bearings, slip rings, nozzles, valves, and the like. Glassy carbon has found use in biomedical applications, such as in the production of heart valves. U.S. Pat. No. 5,458,632 (Preidel) describes glassy carbon structures that are implantable in a clinical environment. Preidel describes low-surface-area glassy carbon electrodes (surface: 0.125 cm.sup.2) which, when incubated with aqueous solutions of tissue-plasminogen activator, are resistant to blood clotting. U.S. Pat. No. 4,612,100 (Edeling) describe implantable electrodes produced by sputtering of glassy carbon on a part of a surface of an electrode to be implanted. Stimulating electrodes, that is, heart pacers, are mentioned.
U.S. Pat. No. 5,118,403 (Magee) describe a linear array electrode for use in a flowcell detector. A dicing saw is used to create an array of parallel grooves in a surface of a glassy carbon layer to form an array element. The resultant, grooved article is embedded in an electrically-insulating material such that the surface of each ridge (between each groove) is exposed. The exposed, linear, parallel ridges, each having a width in the range of 10-100 microns, defines the array.
These and other techniques for the use of glassy carbon, including the production of small-scale devices, are useful in some circumstances. However, these techniques typically involve more than a desirable number of fabrication steps, and in many cases it would be advantageous to reduce the cost, and increase versatility, associated with these techniques. Additionally, micromachining or other destructive techniques for creating a desired shape in glassy carbon is difficult to perform accurately due to the brittle nature of glassy carbon, which derives its name from its fracture behavior, i.e., a behavior similar to that of glass.
Carbon fibers are known for many small-scale applications. Carbon fibers are very strong, but the tailorability of mechanical and electrical properties of carbon fibers is limited. Additionally, carbon fibers cannot readily be formed into a variety of shapes.
Accordingly, it is an object of the invention to provide a technique for forming high-carbon solid structures on the micro- and nanoscale conveniently, inexpensively, and reproducibly.